I’m starting to level a Fire Mage and my goodness you guys have a metric ton of AoE options available.
I can’t decide which ones to run down; just using Ignite spreads, Flamestrike talents, or Living Bomb.
I want to kind of use Flamestrike, but I kind of want to do heavy cleave damage instead of splooching all over the floor…
It doesn’t matter what you choose because all of them suck right now 
Fire Mage is so bad it’s worse than augmentation evoker.
I would just go a flamestrike build and use combustion after all mobs are gathered. It does alot of damage . Fire is not useless , and still viable. it does struggle on M+ relying on combustion but on raids its fine ( im able to clear normal and heroic raids so far doing good damage).